We are talking about 2 different types of bone scans here.

One is a Bone Density which is done on healthy women (or man) and people who have RSD. This scan does not involve having a dye injected. I've had 4 of these done to check for osteoporosis.

The second scan is a Tri-Phasic Bone Scan which is done when docs suspect you have RDS. The sensitivity is 50-60%.
It involves injection of a radioactive tracer (dye) with scans done early after the injetion of dye and hours later, looking for increased or decreased uptake of the dye, which is indicative of RSD, but you can have RSD even if it is negative and not have RSD if it is positive.
(It can also show osteopenia)

I've had two of these. The first was positive and the second was negative.
This is a very helpful finding IF a doctor knows what that means.

What doctors don't usually know is that this is normal for people WITH RSD.

Quote from: http://podiatry.curtin.edu.au/encyclopedia/crps1

"Three phase bone scan: ... this is only sensitive within the first 20-26 weeks of the onset of CRPS and after 26 weeks there is a poor correlation. Even at 26 weeks the sensitivity is only 50% (Dilnot, 1998).

A quote from http://www.rsds.org/5/news/2005/bonescans.htm :

"....in the recent volume of Progress in Pain Research and Management1, only 16 percent of the patients diagnosed with CRPS/RSD 8 weeks after trauma had the characteristic bone scan pattern."
In only half the cases, the bone scan pattern was pathognomonic of CRPS/RSD I.
Furthermore, as the disease progresses, the changes in the bone scan go away.

Quote from Duke Orthopedics: http://www.ispub.com/ostia/index.php...vol2n1/cps.xml

Three phase bone scan demonstrates distinctive pattern of radiotracer uptake. Early stages shows increase in blood flow, whereas late stages shows total decrease in blood flow. The diagnostic sign is periarticular pooling specially in the late phase of the scan. However this is only sensitive within the first 20-26 weeks of the onset of CRPS and after 26 weeks there is a poor correlation. Even at 26 weeks the sensitivity is only 50%.

A three phase bone scan may demonstrate a reduction of blood flow during the early stages but does show increased peri-articular uptake during the third stage. "

Bone changes - X-rays may show wasting of bone (patchy osteoporosis) or a bone scan may show increased or decreased uptake of a certain radioactive substance (technecium 99m) in bones after intravenous injection http://www.rsdfoundation.org/en/en_c...uidelines.html